1. Field of the Invention
The present invention generally relates to an image processing system, and more particularly to an adaptive color correction system adaptable to a dual-mode image device.
2. Description of Related Art
In an imaging system, lens shading is a phenomenon that causes pixels located away from a center pixel of a pixel array to have a lower pixel signal value even when all pixels are exposed to the same illumination condition. As a result, brightness of an image falls off from center to corners. In other words, maximum brightness may be at or around the center but fall along a radius of the pixel array. The lens shading phenomenon may be resulted, for example, from lens mechanism, optics, sensor pixels, ray traveling distance, aperture effect or ray incident angle to pixels.
Lens shading correction (LSC) is thus commonly proposed to compensate for the brightness falloff by applying different gains, particularly for the pixels away from the center of the pixel array.
A complementary metal-oxide-semiconductor (CMOS) image sensor not only senses radiance in visible band but also radiance in near-infrared (IR) band. An IR-cut filter is used to pass the visible band wavelengths and block IR band wavelengths, such that discoloration caused by IR band wavelengths may be avoided. In some applications like surveillance, however, artificial IR light may be applied to increase visibility in low-light condition. To receive IR band signals in low light with the artificial IR light and avoid discoloration in normal light scene without the artificial IR light, a dual-band IR-cut filter may be used.
Color correction is commonly applied in an image processing system in order to correct for color distortion. A need has arisen to propose a novel color correction scheme that is adaptable to some applications like surveillance.